Keel stepped mast conversion

Hi, Just saw an add for a new mast on Craig's list and that got me thinking... would it be feasible to convert a Cal 29 to a keel stepped mast and what would such a project involve? My interest is purely theoretical at this point, just would like to hear your thoughts on the subject. Cheers,

First off, WHY? How is this mod going to make your boat or your sailing experience better. Pros: Some believe when you roll your boat offshore and snap the rig off you're more likely to have a stub left. You can go with a thinner walled mast, since it will be a fixed/pin column, so less weight aloft. http://www.ecourses.ou.edu/cgi-bin/ebook.cgi?doc=&topic=me&chap_sec=09.2&page=theory Are you going offshore? Is this mast lighter than the one you have? You could probably reduce almost as much weight aloft by going with Dynex Dux rigging with a lot less effort and cost. Cons: A lot of work. A lot of money. Ruining resale value of boat. Keel stepped masts almost invariably leak rainwater into the cabin. If you just want that as a new mast, cut it down to the same length as what you currently have. John From: Alex Kunadze <kr… [at] gmail.com> To: Ca… [at] yahoogroups.com Sent: Wednesday, March 20, 2013 2:03 PM Subject: [Cal_Boats] Keel stepped mast conversion Hi, Just saw an add for a new mast on Craig's list and that got me thinking... would it be feasible to convert a Cal 29 to a keel stepped mast and what would such a project involve? My interest is purely theoretical at this point, just would like to hear your thoughts on the subject. Cheers,

Hehe, thanks for the info and the link John. A bit too much math for me, but it might come in handy one day :) I'm not really considering doing this, just wondering what the pros, cons and gotchas would be. It's a fun way to spend the time :) As to why, I was under impression that keel-stepped masts are inherently more stable and rigid, especially in cases of shroud failure. I'm not worried about weight that much. And no, I'm not going offshore, but one can dream :) Cheers, Alex. On Wed, Mar 20, 2013 at 4:40 PM, John Courter <ca… [at] yahoo.com> wrote: > ** > > > First off, WHY? How is this mod going to make your boat or your sailing > experience better. > > Pros: > Some believe when you roll your boat offshore and snap the rig off you're > more likely to have a stub left. > You can go with a thinner walled mast, since it will be a fixed/pin > column, so less weight aloft. > > http://www.ecourses.ou.edu/cgi-bin/ebook.cgi?doc=&topic=me&chap_sec=09.2&page=theory > > Are you going offshore? Is this mast lighter than the one you have? You > could probably reduce almost as much weight aloft by going with Dynex Dux > rigging with a lot less effort and cost. > > Cons: > A lot of work. > A lot of money. > Ruining resale value of boat. > Keel stepped masts almost invariably leak rainwater into the cabin. > > > If you just want that as a new mast, cut it down to the same length as > what you currently have. > > John > > > ------------------------------ > *From:* Alex Kunadze <kr… [at] gmail.com> > *To:* Ca… [at] yahoogroups.com > *Sent:* Wednesday, March 20, 2013 2:03 PM > *Subject:* [Cal_Boats] Keel stepped mast conversion > > > Hi, > Just saw an add for a new mast on Craig's list and that got me thinking... > would it be feasible to convert a Cal 29 to a keel stepped mast and what > would such a project involve? My interest is purely theoretical at this > point, just would like to hear your thoughts on the subject. > Cheers, > > > >

What comes to my mind is where are the forces going. There are considerable forces down on the mast. If you keel step it, do you have a beam there to support the load? The design of the boat carries that load from the base of the mast to the deck, or bulkheads, or whatever but the point is it was designed to take the load the way it was built. On my boat, I have a 6x8 piece of very hard wood 5 feet long that takes the load to about 6 floors that spread that load over a large part of the hull. You risk putting a load somewhere that cannot take it. Allen On Wed, Mar 20, 2013 at 4:57 PM, Alex Kunadze <kr… [at] gmail.com> wrote: > ** > > > Hehe, thanks for the info and the link John. A bit too much math for me, > but it might come in handy one day :) > > I'm not really considering doing this, just wondering what the pros, cons > and gotchas would be. It's a fun way to spend the time :) > > As to why, I was under impression that keel-stepped masts are inherently > more stable and rigid, especially in cases of shroud failure. I'm not > worried about weight that much. > And no, I'm not going offshore, but one can dream :) > > Cheers, > Alex. > > > On Wed, Mar 20, 2013 at 4:40 PM, John Courter <ca… [at] yahoo.com> wrote: > >> ** >> >> >> First off, WHY? How is this mod going to make your boat or your sailing >> experience better. >> >> Pros: >> Some believe when you roll your boat offshore and snap the rig off you're >> more likely to have a stub left. >> You can go with a thinner walled mast, since it will be a fixed/pin >> column, so less weight aloft. >> >> http://www.ecourses.ou.edu/cgi-bin/ebook.cgi?doc=&topic=me&chap_sec=09.2&page=theory >> >> Are you going offshore? Is this mast lighter than the one you have? You >> could probably reduce almost as much weight aloft by going with Dynex Dux >> rigging with a lot less effort and cost. >> >> Cons: >> A lot of work. >> A lot of money. >> Ruining resale value of boat. >> Keel stepped masts almost invariably leak rainwater into the cabin. >> >> >> If you just want that as a new mast, cut it down to the same length as >> what you currently have. >> >> John >> >> >> ------------------------------ >> *From:* Alex Kunadze <kr… [at] gmail.com> >> *To:* Ca… [at] yahoogroups.com >> *Sent:* Wednesday, March 20, 2013 2:03 PM >> *Subject:* [Cal_Boats] Keel stepped mast conversion >> >> >> Hi, >> Just saw an add for a new mast on Craig's list and that got me >> thinking... would it be feasible to convert a Cal 29 to a keel stepped mast >> and what would such a project involve? My interest is purely theoretical at >> this point, just would like to hear your thoughts on the subject. >> Cheers, >> >> >> > >

I was wondering about that... There is a mast support beam under the deck sole, and a teak post that transfers the loads from the mast to that beam. There's also the bulkhead, but it would transfer the load from the deck to approximately the same area of the hull as the beam. I wonder how much load does the deck itself absorb, given that it's rigidly connected to the bottom of the hull... Cheers, Alex. On Wed, Mar 20, 2013 at 5:09 PM, Allen Edwards <al… [at] gmail.com>wrote: > ** > > > What comes to my mind is where are the forces going. There are > considerable forces down on the mast. If you keel step it, do you have a > beam there to support the load? The design of the boat carries that load > from the base of the mast to the deck, or bulkheads, or whatever but the > point is it was designed to take the load the way it was built. On my > boat, I have a 6x8 piece of very hard wood 5 feet long that takes the load > to about 6 floors that spread that load over a large part of the hull. You > risk putting a load somewhere that cannot take it. > > Allen > > > On Wed, Mar 20, 2013 at 4:57 PM, Alex Kunadze <kr… [at] gmail.com> wrote: > >> ** >> >> >> Hehe, thanks for the info and the link John. A bit too much math for me, >> but it might come in handy one day :) >> >> I'm not really considering doing this, just wondering what the pros, cons >> and gotchas would be. It's a fun way to spend the time :) >> >> As to why, I was under impression that keel-stepped masts are inherently >> more stable and rigid, especially in cases of shroud failure. I'm not >> worried about weight that much. >> And no, I'm not going offshore, but one can dream :) >> >> Cheers, >> Alex. >> >> >> On Wed, Mar 20, 2013 at 4:40 PM, John Courter <ca… [at] yahoo.com>wrote: >> >>> ** >>> >>> >>> First off, WHY? How is this mod going to make your boat or your >>> sailing experience better. >>> >>> Pros: >>> Some believe when you roll your boat offshore and snap the rig off >>> you're more likely to have a stub left. >>> You can go with a thinner walled mast, since it will be a fixed/pin >>> column, so less weight aloft. >>> >>> http://www.ecourses.ou.edu/cgi-bin/ebook.cgi?doc=&topic=me&chap_sec=09.2&page=theory >>> >>> Are you going offshore? Is this mast lighter than the one you have? >>> You could probably reduce almost as much weight aloft by going with Dynex >>> Dux rigging with a lot less effort and cost. >>> >>> Cons: >>> A lot of work. >>> A lot of money. >>> Ruining resale value of boat. >>> Keel stepped masts almost invariably leak rainwater into the cabin. >>> >>> >>> If you just want that as a new mast, cut it down to the same length as >>> what you currently have. >>> >>> John >>> >>> >>> ------------------------------ >>> *From:* Alex Kunadze <kr… [at] gmail.com> >>> *To:* Ca… [at] yahoogroups.com >>> *Sent:* Wednesday, March 20, 2013 2:03 PM >>> *Subject:* [Cal_Boats] Keel stepped mast conversion >>> >>> >>> Hi, >>> Just saw an add for a new mast on Craig's list and that got me >>> thinking... would it be feasible to convert a Cal 29 to a keel stepped mast >>> and what would such a project involve? My interest is purely theoretical at >>> this point, just would like to hear your thoughts on the subject. >>> Cheers, >>> >>> >>> >> > >

Pretty much all the rig tension mast compression loads are tied together by the beam, bulkhead, compression post to shrouds and mast. All I think what's left is the heeling forces for the deck and hull to deal with. My guess on keel stepped masts staying up with shroud failures was probably more true with solid tree trunk masts. Here's a discussion on the topic: http://www.cruisersforum.com/forums/f47/what-is-the-advantage-of-a-keel-stepped-mast-5733.htmlhttp://www.cruisersforum.com/forums/f47/what-is-the-advantage-of-a-keel-stepped-mast-5733.html From: Alex Kunadze <kr… [at] gmail.com> To: Ca… [at] yahoogroups.com Sent: Wednesday, March 20, 2013 5:44 PM Subject: Re: [Cal_Boats] Keel stepped mast conversion I was wondering about that... There is a mast support beam under the deck sole, and a teak post that transfers the loads from the mast to that beam. There's also the bulkhead, but it would transfer the load from the deck to approximately the same area of the hull as the beam. I wonder how much load does the deck itself absorb, given that it's rigidly connected to the bottom of the hull... Cheers, Alex. On Wed, Mar 20, 2013 at 5:09 PM, Allen Edwards <al… [at] gmail.com> wrote: > >What comes to my mind is where are the forces going. There are considerable forces down on the mast. If you keel step it, do you have a beam there to support the load? The design of the boat carries that load from the base of the mast to the deck, or bulkheads, or whatever but the point is it was designed to take the load the way it was built. On my boat, I have a 6x8 piece of very hard wood 5 feet long that takes the load to about 6 floors that spread that load over a large part of the hull. You risk putting a load somewhere that cannot take it. > > >Allen > > > >On Wed, Mar 20, 2013 at 4:57 PM, Alex Kunadze <kr… [at] gmail.com> wrote: > > >> >>Hehe, thanks for the info and the link John. A bit too much math for me, but it might come in handy one day :) >> >> >>I'm not really considering doing this, just wondering what the pros, cons and gotchas would be. It's a fun way to spend the time :) >> >> >>As to why, I was under impression that keel-stepped masts are inherently more stable and rigid, especially in cases of shroud failure. I'm not worried about weight that much. >>And no, I'm not going offshore, but one can dream :) >> >>Cheers, >>Alex. >> >> >> >>On Wed, Mar 20, 2013 at 4:40 PM, John Courter <ca… [at] yahoo.com> wrote: >> >> >>> >>>First off, WHY? How is this mod going to make your boat or your sailing experience better. >>> >>> >>>Pros: >>>Some believe when you roll your boat offshore and snap the rig off you're more likely to have a stub left. >>>You can go with a thinner walled mast, since it will be a fixed/pin column, so less weight aloft. >>>http://www.ecourses.ou.edu/cgi-bin/ebook.cgi?doc=&topic=me&chap_sec=09.2&page=theory >>> >>> >>> >>>Are you going offshore? Is this mast lighter than the one you have? You could probably reduce almost as much weight aloft by going with Dynex Dux rigging with a lot less effort and cost. >>> >>> >>>Cons: >>>A lot of work. >>>A lot of money. >>>Ruining resale value of boat. >>>Keel stepped masts almost invariably leak rainwater into the cabin. >>> >>> >>> >>> >>>If you just want that as a new mast, cut it down to the same length as what you currently have. >>> >>> >>>John >>> >>> >>> >>> >>> >>>________________________________ >>> From: Alex Kunadze <kr… [at] gmail.com> >>>To: Ca… [at] yahoogroups.com >>>Sent: Wednesday, March 20, 2013 2:03 PM >>>Subject: [Cal_Boats] Keel stepped mast conversion >>> >>> >>> >>> >>>Hi, >>>Just saw an add for a new mast on Craig's list and that got me thinking... would it be feasible to convert a Cal 29 to a keel stepped mast and what would such a project involve? My interest is purely theoretical at this point, just would like to hear your thoughts on the subject. >>>Cheers, >>> >>> >>> >> >

On 3/20/2013 8:09 PM, Allen Edwards wrote: > > > What comes to my mind is where are the forces going. There are > considerable forces down on the mast. If you keel step it, do you > have a beam there to support the load? The design of the boat carries > that load from the base of the mast to the deck, or bulkheads, or > whatever but the point is it was designed to take the load the way it > was built. On my boat, I have a 6x8 piece of very hard wood 5 feet > long that takes the load to about 6 floors that spread that load over > a large part of the hull. You risk putting a load somewhere that > cannot take it. Most fiberglass boats are carefully engineered to distribute forces as needed, with tension rods commonly used now to take the load of shrouds. I imagine that if you converted a deck-stepped rig to a keel-stepped one, you'd need to add something like that to take the shroud loads down to the new mast step. Then you'd have to reinforce the deck in the way of the mast--the "mast partners"--to take the horizontal loads imposed by the mast itself, especially if it's subjected to bending, and of the shrouds and tension rods. For me, a person who's not an engineer, when I need to address forces like that, my reaction is to build in the strength I think I need, and then triple it. It's the old belt and suspenders approach, and ends up being three times as heavy as necessary. Or, if I've guessed wrong, maybe not heavy enough. Oops. It's why people with engineering knowledge design these things now. Chris Campbell > >